This invention relates broadly to a winching device for lifting a load and, in particular, to a cable guide for a winch, for guiding the cable smoothly onto the lifting drum of the winch.
A winch, as herein referred to, is a stationary device for lifting a load while a hoist, on the other hand, is a device that can be moved from place to place, as for example, on a wheeled trolley or the like. A winch typically includes a lifting drum about which a wire rope (cable) is wound to raise a load. The drum may be turned either manually or by a motor acting through a gear or sprocket and chain drive system. A racket and pawl mechanism is typically connected to the drive system to prevent the load from slipping as it is being raised. Larger winches are also equipped with brakes that operate to hold the load at a desired elevated position, thereby removing the load from the lifting system.
Most larger winches employ cable guides positioned at either end of the lifting drum to engage the cable as it reaches the end of a complete wrap and begins to reverse the direction of wrap back towards the opposite end of the drum. One such prevalent guide is an elongated metal cylinder that is located at each end of the drum. Each cylinder is mounted perpendicular to the axis of the drum and is arranged to contact the cable as it reaches the end of a wrap, taking some of the load from the cable and thus enhancing the cable's ability to reverse direction.
The lifting drum is generally equipped with radially expanded end flanges of ten times, the cable training over the cylindrical guide will wrap upon itself a number of times before it starts back in the opposite direction. As a result, when the wire rope finally reverses direction, it jumps down onto the last completed wrap, thus stressing or shocking the cable. When the load being lifted is high, the shock to the wire rope is correspondingly high and can, under certain conditions, shorten the life of the cable or cause damage to the lifting mechanism. Similarly, the cable only makes a single point contact with the cylindrical guide roller as it trains over the roller. This, coupled with the fact that the cable and the cylinder are in metal to metal contact, further acts to shorten the life of the cable.
Other guide systems have also been devised, such as follower systems of the type employed in high priced fishing reels, having a traveler that moves back and forth across the drum to continuously control the wrapping of the line in response to the rotational speed of the drum. Although these follower systems work well in practice, they are rather impractical for use in heavy duty winches because of the high line pulls involved and the expense involved in manufacturing and maintaining the device.
Simple ring systems are also known and used in the art, wherein a steel ring is welded to the end flange of the lifting drum and the cable allowed to run through the loop onto the drum. Although inexpensive, this type of system produces relatively high loads on the cable and again creates a single point running contact between the ring and the cable. Although this loop system is relatively simple and inexpensive, it is subject to early failure and produces less than satisfactory wrapping of the wire rope about the drum.